Data

Volume of thiosulphate = 200cm³ (0.2dm³)
Molar volume at S.T.P = 22.4dm³/mole
Asked: The mass of Sulphur formed

The balanced chemical equation for the reaction.
Na₂S₂O_3(aq)+ 2HCL_(aq) → 2NaCL_(aq) + H₂O_(l) +S_(s) SO_2(g)

mass of Sulphur formed:

convert o.2dm³ of Na₂S₂O₃ into moles
Mole = volume (dm³) / molar volume (dm³/mole)
= 0.2dm³ / 22.4dm³/mole
= 0.0089285714 mole of Na₂S₂O₃

make mole equivalent between Na₂S₂O₃ and S
1 mole of Na₂S₂O₃ Ξ 1 mole of S
0.0089285714 mole of Na₂S₂O₃ Ξ ?? of S

= (0.0089285714 mole × 1 mole) / 1 mole
= 0.0089285714 mole of S

convert mole of Sulphur (S0) into mass.

Mole = mass / molar mass
mass = mole × molar mass
= 0.0089285714 × 38g/mole
= 0.2857142848 ≈ 0.29g

0.29g of Sulphur was formed during the reaction.